DISEASES OF PLANTS 233 



But a lemon with blue mold cannot infect the lemons 

 around it, unless their skins are bruised or broken 

 (figure 132). 



The brown rot also differs from blue mold in produc- 

 ing a peculiar odor which attracts swarms of small 

 flies. 



The soil in the orchards is in many cases filled with 

 the spores of brown rot, but if the fruit can be kept from 

 touching the soil (or from being splashed by water 

 from the soil), no rot develops. In some cases a " cover 

 crop " of vetch may protect the fruit by covering the 

 soil closely; in other cases the lowest branches of the 

 tree may be pruned away. 



But it often happens that some of the fruit has the 

 brown rot on it, and the water of the washer in which 

 the lemons are washed becomes infected. 1^ is then 

 necessary to add something to the wash water to kill 

 the fungus. Formalin, bluestone, and permanganate 

 of potash have been used for this purpose with entire 

 success. (California Experiment Station, Bulletin 190, 

 1907.) 



Place some lemons infected with brown rot in a pail 

 of water and wash them thoroughly. Take them out and 

 place some sound lemons in the water; allow them to 

 stand overnight; in the morning take them out and 

 put them aside ; how many develop brown rot ? 



Take out a pint of this water and add to it a teaspoon- 

 ful of formalin; put some sound lemons in it overnight ; 



